Audio signals, especially music signals, usually show repetitive characteristics: an audio section will be repeated later in the audio signal. Detecting these repetitive sections in an audio signal has gained much attention, since it is a fundamental step and can be used in various applications, such as music detection, music chorus detection, music thumbnailing or summarization, and music structure analysis.
With regard to the term repetitive section, different terms with similar meaning may be used in different literatures, such as recurrent, repetition, repetitive pattern, or repeating pattern. These terms may be used interchangeably in this disclosure without any confusion.
To detect the repetitive sections, approaches can involve computing a similarity (or distance) matrix, and finding the repetitive patterns in this matrix. The similarity matrix includes similarity values s(t, l) between frames t and t+l where l represents the offset of similarity values s(t, l). A general idea is to estimate a fixed threshold, and use it to binarize the matrix. That is, each pixel in the similarity matrix is binarized to 1 if its similarity value is larger than the fixed threshold, indicating it represents a repetition; and otherwise the pixel is set to 0. After binarization, repetitive patterns can be easily found by detecting the lines containing continuous 1 in each offset. (See M. Goto. “A chorus-section detecting method for musical audio signals,” Proc. Acoustics, Speech, and Signal Processing, 2003, which is herein incorporated by reference for all purposes)
The approaches described in this section are approaches that could be pursued, but not necessarily approaches that have been previously conceived or pursued. Therefore, unless otherwise indicated, it should not be assumed that any of the approaches described in this section qualify as prior art merely by virtue of their inclusion in this section. Similarly, issues identified with respect to one or more approaches should not assume to have been recognized in any prior art on the basis of this section, unless otherwise indicated.